In order to meet varying users' requirements, many types of luminous keyboards have been developed and introduced to the market to enable users to clearly recognize locations of keys and character notations in a light deficient environment without erroneously striking the keys and entering commands.
U.S. Pat. No. 7,357,523 discloses an illuminating keyboard which comprises a keyboard and a backlight means. The keyboard includes a plurality of keys and a bottom plate. The keys are mounted onto the bottom plate and depressible up and down against the bottom plate. The backlight means is located below the keyboard and includes a light guiding plate, a reflective plate and a light source. The reflective plate is located below the light guiding plate which has a plurality of openings to hold the light source. The light source provides light needed by the keyboard.
R.O.C. patent No. M321551 also discloses an illuminating keyboard which comprises a circuit board, a keyboard, a light guiding plate, a plurality of light emitting diodes (LEDs) and a reflective plate. The circuit board, keyboard and light guiding plate are made of light permeable materials. The circuit board has a plurality of elastic pieces on the surface at one side. The keyboard covers one side of the circuit board where the elastic pieces are located. The keyboard has a plurality of keys corresponding to the elastic pieces. The light guiding plate covers another side of the circuit board with a plurality of opening sets formed thereon corresponding to the keys. The opening sets are interposed by a plurality of housing troughs to hold the LEDs. The reflective plate is bonded to another surface of the light guiding plate to reflect light emitted from the LEDs upwards to the keys.
The openings on the aforesaid light guiding plate are respectively formed in a rectangular shape and each has four side walls perpendicular to each other. The side walls are served as light incident surfaces of the light entering the light guiding plate. In practice, the light refracted by the side walls cannot be fully transmitted in the light guiding plate, hence is not fully refracted to the light guiding plate to generate sufficient luminosity on the keycaps. In such a structure, in order to generate equal luminosity on the keys, the distance between the openings has to be shortened, hence more lighting elements are needed. As a result, production cost is higher.